ECCMID17: DNA fingerprinting suggests food may be a source of C. difficile

In new research presented at the 27th European Congress of Clinical Microbiology and Infectious Diseases (April 22–25, Vienna), scientists have utilized DNA fingerprinting to track strains of C. difficile, suggesting that food may be a potential source.

C. difficile is a common infection in hospitals; it is associated with issues around antibiotic resistance and can be fatal in some patients. Presenter of the new study, David Eyre (University of Oxford, UK) explained: “We know that C. difficile live in the gut in a small proportion of healthy people, where it causes no symptoms. However, its resistance to antibiotics means it can grow uncontrollably in patients treated with the drugs, causing diarrhoea that can be severe or even fatal. It is the most frequent cause of infectious diarrhoea in hospitalized patients, and the increase in the use of antibiotics has allowed C. difficile to spread more effectively”

“Lots of effort has gone into controlling its spread including infection control interventions such as hand washing campaigns, and reducing the use of antibiotics that can lead to infection. Despite these measures people are still getting C. difficile infections and the routes of transmission are not completely understood.”

The team utilized DNA fingerprinting to examine the types of C. difficile causing infections in patients and also investigate their distribution throughout Europe.

Eyre and his team analyzed stool samples submitted from 482 European hospitals on 1 day in the summer, and 1 in the winter. The group then selected the ten most common types of C. difficile discovered in the samples and utilized DNA fingerprinting to examine their distribution both within and between countries.

The researchers discovered that while some strains were clustered within particular countries, suggesting the well-known transmission via hospitals, some strains were dispersed across countries, suggesting alternative modes of transmission. This led the authors to hypothesize that transmission via food could be included in the transmission of these widely dispersed strains.

Eyres commented: “We know that C. difficile infection can spread within hospitals. If this was the only route of transmission, we would expect to see each type of bacteria was concentrated within one area. However, because we also saw some types that were spread around several countries, this suggests the bacteria are moving around by other means”

The study indicated five of the strains were clustered within countries, whereas five were not. Eyre continued; “We don’t know much about how C. difficile might be spread in the food chain, but this research suggests it may be very widespread. If it turns out to be the case, then we need to focus on some new preventative strategies such as vaccination in humans, once this is possible, or we might need to look at our use of animal fertilizers on crops.”

Eyre and his team hope to repeat this study but also include samples from food, the wider environment and hospitals, in order to further elucidate the sources of C. difficile infection. Eyre concluded: “This study doesn’t give us any definitive answers, but it does suggest other factors are at okay in the spread of C. difficile and more research is urgently needed to pin them down.”